It is proposed to investigate the endocrine aspects of calcium homeostasis along the following lines: (1) a study of the regulation of the renal-vitamin D endocrine system in Japanese quail, particularly with respect to role of the hormones of the gonadal, pituitary, and parathyroid glands; (2) a study of the vitamin D metabolism in poikilotherms (fishes, amphibia, reptiles); (3) a survey of the plasma gonadal hormone (estradiol, progesterone, testosterone) in the Japanese quail; and (4) a study of the bioassayable parathyroid hormone-like material in urines from hypercalcemic cancer patients. BIBLIOGRAPHIC REFERENCES: Kenny, A.D. Vitamin D metabolism: physiological regulation in egg laying Japanese quail. Amer. J. Physiol. 230, 1609-1615 (1976). Dacke, C.G., Furr, B.J.A., Boelkins, J.N. and Kenny, A.D. Sexually related changes in plasma calcitonin levels in Japanese quail. Comp. Biochem. Physiol. 55A, 341-344 (1976).